National Climatic Data Center, 11 May 2001

U.S. Drought Highlights:

• On the national scale, severe drought affected about seven percent of the contiguous United States as of the end of April 2001
• Drought continued in the Pacific Northwest and Southeastern U.S.
• Second dry month in a row in the Ohio Valley
• April very dry in the Northeast

Contents Of This Section:

• National Overview
• Palmer Drought Indices
• Regional Drought Watch:
  • Standardized Precipitation Index
  • Regional Overview
  • Western U.S. Drought
  • Southeast and Southern Plains Drought
  • Central Region Dryness
  • Northeast Region Dryness
• Additional Contacts

• severe drought affected about seven percent of the contiguous United States as of the end of April 2001;
• the total drought area has held steady at about 7 to 15 percent for the last seven months (see graph below left);
• the coverage of the current drought peaked in August 2000 at about 36% of the contiguous U.S., which was as extensive as the major droughts of the last 40 years, but not as large as the "dust bowl" droughts of the 1930's and 1950's;
• on a broad scale, the last two decades were characterized by unusual wetness with short periods of extensive droughts, whereas the 1930's and 1950's were characterized by prolonged periods of extensive droughts with little wetness (see graph below right);
• although different parts of the U.S. have experienced unusually wet conditions during the last 19 months, there continues to be little change in the overall national wetness picture;
• the percentage of the nation severely wet has held steady at about five to ten percent during this period (see graph below left).

• the short-term soil moisture conditions as calculated by the National Weather Service,
• the statewide reports of percent of the topsoil very dry ("short" to "very short") provided by the U.S. Department of Agriculture,
• the satellite observations of surface wetness anomalies, and
• the USGS April daily streamflow maps.

• NOAA satellite observations of vegetation health revealed increasing stress on vegetation in parts of the West.
• The Keetch-Byram Drought Index (KBDI) is used by the National Interagency Fire Center to monitor the risk of wildfires. The KBDI showed a drying trend along the Gulf and South Atlantic coasts with an increasing threat of wildfires across Florida and in parts of the West by the end of April. The Forest Service fire danger analysis indicated a continuing risk of wildfires in the Southwestern U.S. and an increasing threat of wildfires in the northern High Plains and the southern Great Lakes.

The seven maps below show the April 2001 spatial patterns of SPI for seven different periods ranging from one month (short-term conditions) to 24 months (long-term conditions). When taken together, they give a combined geographical and temporal picture of the severity of precipitation anomalies. The maps illustrate, for example:

• short-term (1-month) dryness affected the Northeast, coastal Mid-Atlantic, Southeast, and southern Plains states but above-normal precipitation in March resulted in a neutral (mid-range) SPI in these regions for the 2-month period;
• short-term (2-month) dryness was centered in the Ohio Valley and spread northward to the Great Lakes and south and westward to Tennessee and Oklahoma. The lack of precipitation was exacerbated by unusually warm April temperatures in this region;
• March and April rains brought short-term relief to the Pacific Northwest, but longer-term (3-month to 24-month) drought still affects much of the Pacific Northwest and northern Rockies; and
• the Southeast, Ohio Valley, and parts of the Northeast suffer from long-term drought.

• 19th wettest April,
• third driest rainy season (October-April),
• third driest May-April,
• second driest November-April (see graph below right), second only to the record drought of 1976-77.

The well below normal reservoir levels and mountain snowpack are having a major impact on water supplies. Severe agricultural impacts have been noted in parts of Oregon and northern California. A potentially severe wildfire season is of concern to those in the Pacific Northwest.

• nine of the last 12 months averaged below to much below normal (see graph below left),
• ninth driest May-April on record,
• third consecutive year with below-average May-April precipitation,
• short-term (April) precipitation across the region was variable from state to state,
• on the long-term (May-April) the region was predominantly dry,
• the southern Appalachian Mountains of western North Carolina have suffered from persistent drought for the last three years.

Conditions in Florida were especially severe:

• April saw a return to dry conditions following a short reprieve in March,
• statewide Palmer Index continued in the severe drought category,
• third driest May-April on record,
• third consecutive May-April with below-average rainfall,
• wildfires closed major highways in southern Florida,
• since January 1st, more than 2200 wildfires have charred 178,138 acres in the state.

• 20th driest April,
• tenth driest March,
• seventh driest March-April in the 1895-2001 record (see graph below right),
• six of the last seven months have been drier than normal, resulting in the ninth driest October-April.

The heavy snow cover at the beginning of the month rapidly melted and was nearly gone by late April. Unusually warm temperatures during late April and early May increased the threat of fire danger to parts of the region, especially Maine, which had the driest April and seventh driest February-April.

For additional information on the 2001 wildfire season please see the National Interagency Fire Center web site or the U.S. Forest Service Fire and Aviation web site.

Additional climate monitoring graphics can be found at the Climate Prediction Center's monitoring pages:

• Weekly, Monthly, 3-Month, 12-Month Monitoring
• El Nino, Drought, Snow Cover, and Degree Day Monitoring
• Weekly Drought Monitoring
• Soil Moisture Monitoring